US2795552A

US2795552A - Lubricant compositions

Info

Publication number: US2795552A
Application number: US440265A
Authority: US
Inventors: Andrew D Abbott; John R Thomas; Oliver L Harle
Original assignee: California Research LLC
Current assignee: California Research LLC
Priority date: 1954-06-29
Filing date: 1954-06-29
Publication date: 1957-06-11
Anticipated expiration: 1974-06-11
Also published as: GB796732A

Description

2,795,552 Patented June 11, 1957 LUBRICANT COMPOSITIONS Andrew D. Abbott, Ross, John R. Thomas, Albany, and

Oliver L. Harle, Berkeley, Calif., assignors to California Research Corporation, San Francisco, Caiif, a corporation of Delaware No Drawing. Application June 29, 1954, Serial No. 440,265

14 Claims. 01. 252-490 This invention relates to novel lubricant compositions. More particularly, the invention is concerned with novel lubricating oil compositions having improved oxidation and corrosion inhibiting properties.

Lubricating oils generally have a tendency to deteriorate due to oxidation and form decomposition products which are corrosive to metals. Since lubricating oils in use today almost invariably come into contact with metal surfaces, the problem of overcoming oxidation and corrosion is considered to be one of major importance. Operating conditions encountered in modern internal combustion engines in which these oils are commonly employed involve increased temperatures, higher speeds and reduced clearances which tend to promote decomposition and the formation of corrosive products. Furthermore, these engines generally employ alloy metal bearings which, besides their possible catalytic effect on the decomposition of the hydrocarbon type mineral lubricating oils, are easily corroded and this, in turn, has seriously accentuated the oxidation and corrosion problems in mineral lubricating oils.

Inhibitors have been added to lubricating oils to improve their resistance to decomposition and avoid corrosivity. Mineral lubricating oils for internal combustion engines, due to the severity of their service, have also been compounded with additional agents such as wear inhibitors, sludge inhibitors and detergents to loosen and suspend products of decomposition and counteract their effect. Unfortunately, many of these agents may adversely atfect the efficiency of the oxidation and corrosion inhibitors and it is a problem to find inhibitors which will function in combination with them. Furthermore, some of the most efiective oxidation and corrosion inhibitors contain active sulfur and are, therefore, extremely corrosive to silver and similar metals which are subject to attack by active sulfur. These types of metals, although once not so widely used in contact with lubricating oils and therefore considered to constitute only a minor problem, are being increasingly employed today. Particularly in certain important classes of internal combustion engines as, for example, marine and railroad diesel engines, silver metal-containing bearings are more and more common and the problem of providing proper lubrication for them is one of major importance.

It is, therefore, a general object of this invention to provide lubricating oil compositions having improved antioxidant and anticorrosion properties.

A more particular object of the invention is to provide lubricating oil compositions which are noncor-rosive to silver and similar metals.

Another more particular object is the provision of mineral lubricating oil compositions in which the tendency to corrode alloy bearings of internal combustion engines has been inhibited.

A further and somewhat related object is to provide compounded mineral lubricating oil compositions having improved anticorrosion properties without adversely affecting the stabilizing, deterging and lubricating qualities of the hydrocarbon oil composition.

Another and still more particular object of the invention is the provision of mineral lubricating oil compositions which :are noncorrosive to silver metalcontammg bearings of the type employed in railroad diesel engines.

Additional objects of the invention will become apparent from the description and claims which follow.

In the accomplishment of the above objects, it has been found that compositions comprising an oil of lubricating viscosity and :a complex of molybdic acid with a member of the group consisting of glycols and polyhydroxy benzenes have greatly enhanced anticorrosion properties. It has also been found that, in particular, compositions comprising a compounded mineral lubricating oil for internal combustion engines which is normally corrosive to alloy bearings and such a complex are substantially noncorrosive.

The normal tendency of oils to become oxidized and corrosive is definitely inhibited in the improved compositions of the invention. Metal surfaces in general are not corroded by contact with these compositions and internal combustion engine alloy bearings, in particular, arelremakably benefited. Bearings of silver and similar metals which, as stated above are increasingly important due to their presently expanded use in marine and railroad diesel engines, are not corroded by these compositions whereas conventional oxidation inhibited oils have severely pitted and corroded such bearings. The advantagesof these improvements are obtained in the compositions of this invention without loss of stability or detergency in the composition.

The complexes of molybdic :acid are not only very e fective alone in the oils as primary inhibitors of oxidation but also function in combination with other antioxidants as auxiliary inhibitors. They are, in addition, remark ably effective as metal deactivators for the common bearing metals, such as copper and lead, which normally tend to accelerate the decomposition of lubricating oil compositions.

The molybdic acid complexes of the compositions according to this invention are prepared by the reaction of a mixture of molybdic acid and glycol or polyhydroxy benzene. The mixtures are ordinarily heated to acceler'ate the reaction. Although the nature of the reaction is not definitely known, it is believed that two of the hydroxyl groups of a single glycol or polyhydroxy benzene react with the molybdic acid to form what is commonly termed a metal chelate compound. These compounds are characterized by a claw type of structure in which one or more rings of similar or unlike structure due to the use of mixed glycols or polyhydroxy benzenes are formed including the molybdenum.

The glycols which are reacted with the molybdic acid are preferably ozand fi-alkane diols containing from 2 to 18 carbon atoms. Such glycols include, for example, ethylene glycol, 1,2- and 1,3-propanediol, 1,3-pentanediol, 2,3-butanediol, 1,2-hexanediol, Z-methyl-1,3-pentane-diol, 1,2- and 1,3-octylene glycols including 2-ethylhexane-1,3- diol, 1,2-dodecanediol, 2,4-diethyl-octane-1,3-diol, and 2,4,6-triethyl-decane-1,3-diol. The glycols containing from 6 to 10 carbon atoms are more preferred since they impart an optimum degree of oil solubility to the molybdate. 0L- and B-octylene glycols such as 2-ethylhexane- 1,3-diol have been found to be the most satisfactory for present purposes since they give unusually effective oxidation and corrosion inhibitors.

The polyhydroxy benzenes are preferably vicinal dihydric phenols such as catechol, 3,4-dihydroxy toluene, tert.butylcatechol, cetylcatechol, and the like. They may contain additional hydroxyl groups, as for example, 1,2,4- trihydroxy benzene. Alkyl catechols containing from 2 molybdanyl chloride. 1

to 18 carbon atoms in the alkyl group preferred since the molybdates prepared from them possess the most satisfactoryjoil solubility characteristics.

-Although itis convenient for the sake of illustration to refer to the reaction of molybdic acid with the glycolor polyhydroxy benzene or mixtures thereof to form the complexes 'for the lubricating oil compositions of this invention, other molybdic acid compounds may also be employed. Such compounds include molybdic anhydride, ammonium molybdate, ammonium para-molybdate and The complex of molybdic acidwith glycol or polyhydroxy benzene is present in the compositions of the invention in an amount at'least suflicient to inhibit corrosion or oxidationf Small amounts, usually from about 0.01, to about 5.0 percent by weight based on the oil, ,are'eftective. Proportions ranging from about 0.05 to about 1.0 percent are preferred in most lubricating oil compositions. Concentrates" containing larger proportions, up to SOpercent, either in solution or suspension, are particularly suitable in compounding operations.

Any of the well known types of oils of lubricating viscosity are suitable base oils for the compositions of the invention. They include hydrocarbon or mineral lubrieating oils of naphthenic, parafl5nic,land 'mixedfnaphthenic and pa'raifinic types. They may be refined by any of theconventional methods such as solvent refining and acid refining. Synthetic hydrocarbonioils of the alkylene polymer type or those derived'from coal and shale may also be employed. Alkylene oxide polymers and their derivatives such as the propylene oxide' polymers and their ethyl esters and acetyl derivatives in which the 'terminal hydroxyl groups have been modified are also suitable. Synthetic oils of the dicarboxylic acid ester type including dibutyl adipat e, di-Z-ethylhexyl sebacate, di-nhexyl fumaric polymer,di-lauryl acylate, and the like may be used. Alkyl-benzene types of synthetic oils such as tetradecyl benzene,etci are also included. Liquid esters of acids of phosphorus including tricresyl phosphate, diethyl esters of decane phosphonic acid and the like may also be employed. Also suitable are the polysiloxane oils of the type of polyalkyl-, polyaryl-, polyalkoxyand polyaryloxy siloxanes such as polymethyl siloxane, polymethylphenyl siloxane and polymethoxyphenoxy siloxane and silicate ester oils such as tetraalkyland tetraaryl silicates 'of the tetra-Z-ethylhexyl silicate and tetra-p-tertwbutylphenyl silicate types.

In a preferred embodiment of the invention, as mentioned above, the complexes of molybdic acid with glycol or polyhydroxy benzene are employed in combination with compounded mineral lubricating oils of the internal combustion engine type which are normally corrosive to alloy bearings. In such an embodiment, as in the case of the other, straight oils of lubricating viscosity, a major proportion of the lubricating oil normally corrosive to metals and/or subject to oxidation and a small amount, sufl'icient to inhibit said corrosion and/ or oxidation, of a molybica'cid complex provides a remarkably improved composition. These compounded oils customarily contain detergents such as the oil-soluble petroleum sulfonates and stabilizers such as the metal alkyl phenates. Other agents such as oiliness agents, viscosity index improvers, pour point depressants, blooming agents, peptizing agents, etc. may also be present.

In further illustration of the invention, the following examples are submitted showing the preparation of the molybdic acid complexes and evaluation. of their efiective are at present most lybdic acid remains undissolved. On further heating, a mixture containing the 4-t-butylcatechol molybdate formed solidifies and is collected by filtration. The redbrown solid thus obtained is dissolved in hot methanol and filtered to remove excess molybdic acid. On concentrating the filtrate by evaporation, the 4-t-butylcatechol molybdate crystallizes as garnet-red needles.

Other complexes similar to the above are also prepared by the reaction of molybdic acid with glycols and poly; hydroxy benzenes. The physical properties of these complexes are briefly described in the following table.

The molybdic acid complexes are also conveniently prepared in the form of concentrates suitable for addition to base oils of lubricating viscosity in the preparation of the compositions according to this invention. The following examples are illustrative.

EXAMPLE 2 100 parts of ammonium molybdate, 600 parts of ethylene glycol and 200 parts of toluene are mixed and refluxed with continuous water separation of 17 hours. The refluxed mixture is then transferred to a separatory funnel and the toluene layer is removed. 1Theproduct 'layer along with the excess ethylene glycolis blended into '1000 parts of a lubricating oil mixture consisting of basic calcium petroleum sulfonate and a mineral oil analyzing 4.35 percent by weight total calcium. The excess glycol is then removed by a vacuum distillation.

EXAMPLE 3 122.5 parts of molybdenum trioxide are dissolved in a solution of 190 parts of concentrated ammonium hydroxide (about 28 percent by weight ammonia) in 250 parts of water. This solution is added to 870 parts of 2-ethyl- -l,3-hexane -diol and 260 parts of toluene with constant agitation. The mixture is heated to reflux temperature and the water removed as toluene-water azeotrope.

nessas corrosion inhibitors and antioxidants in oil composition. Unless otherwise specified the proportions given in these examples are on a Weight basis.

EXAMPLE 1 Toluene itself is then'refluxed for about 6 hours during which period an additional small quantity of water is collected. The reaction mixture is filtered to remove unreacted solid material. 325 parts of mineral neutral oil is then' added to the filtrate' and the solution stripped to about C. pot temperature under about 1 mm. Hg pressure. 579 parts of 2-ethyl-1,3-hexane-diol molybdate concentrate analyzing 12.5 percent by weight molybdenum is obtained.

- EXAMPLE '4 .60 parts of solid ammonium molybdate-having the formula (NH4)eMO7024'4I-I2O are added to 348 parts of 2- ethyl-1,3-hexanediol and 130 parts of xylene. The mixture is agitated mechanically and the xylene refluxed for 6 hours during which time the water evolved is separated from the refluxing xylene. The mixture is then filtered to remove unreacted solid material. The filtrate is blended with about 130 parts of mineral neutral oil and stripped to'a pot temperature of about C(at about 1 mm. Hg pressure to give the 2-ethyl 1,3-hexane-'diol molybdate concentrate, v e L EXAMPLE 5 To a mixture of 184 parts of 2-methyl-2,4-pentane-diol and 120 parts of toluene are added 50 parts of crystalline ammonium molybdate of the formula The mixture is agitated mechanically and the toluene refluxed for about 12 hours during which time the water evolved is separated from the refluxing toluene. The reaction mixture is filtered to remove solid unreacted material and the filtrate is stripped of toluene and unreacted 2-methyl-2,4-pentane-diol by heating to about 95 C. under a pressure of about I'm. Hg. The 2- methyl-2,4-pentane-diol molybdate thus obtained is then blended with a base oil containing basic calcium petroleum sulfonate and a heavy metal alkyl phenate.

EXAMPLE 6 144 parts of molybdenum trioxide are dissolved in a solution of 285 parts of water and 225 parts of concentrated ammonium hydroxide containing about 28 per cent by weight ammonium. This solution is added gradually to 450 parts of 2,3-butane-diol and 100 parts of toluene. The mixture is constantly agitated and the toluene refluxed as in the above examples to remove the water over a period of about 6 hours. Solid unreacted materials are removed by filtration. The filtrate is then added e to a concentrated solution of a basic calcium petroleum sulfonate in mineral neutral oil to give two moles of molybdenum for every three moles of calcium present. The mixture is then stripped free of solvent and unused glycol to obtain a 2,3-butane-diol molybdate concentrate.

The effectiveness of the lubricating oil compositions of the invention is demonstrated by the copper-lead strip corrosion test. In this test a polished copper-lead strip is weighed and immersed in 300 cc. of test oil in a 400- milliliter lipless Erlenmeyer beaker. The test oil is maintained at 340 F. and stirred with a mechanical stirrer at 1000 R. P. M. After two hours a synthetic naphthenate catalyst is added to provide the following catalytic metals:

Percent by weight The test is continued 20 hours. The copper-lead strip is then removed, rubbed vigorously with a soft cloth and weighed to determine the net weight loss.

The test oils in this instance include 'both a mineral lubricating oil which is an acid refined medicinal type White mineral oil and a compounded mineral lubricating oil of the internal combustion engine type which is normally corrosive to alloy bearings. In this case the compounded oil (A) consists of a solvent refined SAE 40 mineral lubricating oil base having a viscosity index of 60 and containing millimoles per kilogram of neutral calcium petroleum sulfonate and 20 millimoles per kilogram of calcium alkyl phenate. Compounded oil (B) consists of the same base oil but contains 28 millimoles per kilogram of a basic calcium petroleum sulfonate. Compounded oil (C) is the same except that 40 millimoles per kilogram of the basic calcium petroleum sulfonate were employed. The results of the tests are shown in the following table. The concentrations of molybdic acid complex employed are given in millimoles of molybdenurnper kilogram of oil.

Table' II COPPER-LEAD ,S'IRIPCORROSION .TEST

. Copper- Lead Additive Base Oil Strip Weight Loss 3-) None Mineral lub. oil- 58. 5 mM./kg. 2-ethyl-1,3-hexaue-d1ol Same 14. 0

moiyb a 20dII%M./kg. 4-t-butylcatechol molyb- Same 2. 5

a e. None compounded Oil A- 253. 1 2 mM./kg. ethylene glycol molybdate Same 7. 3 2 mMJkg. 2-ethy1-1, 3-hexane-diol 7. 0

molybdate. 20 mM./kg. 2ethyl-1, 3-11exane-diol 0. 9

molybdate. 20 mMJkg. Z-methyl-l, 3-pentane-diol 2. 3

.molybdate. 20drn%M./kg. 4-t-butylcatechol molyb- 2. 2

a e.' None 219.0 20 mM./kg. ethylene glycol molybdate. S 1. 9 20 rnlVL-lkg. 2-ethyl-l,3-hexane-d.iol 3. 0

molybdate. 2O mM./kg. 2-3 butanediol molybdate compounded Oil O 2.6

As shown by theabove testdata, straight minerallubrieating-oil alone gave a copper-lead strip weight loss due to corrosion of over 5 8 milligrams in the 20-hour period. By way of distinction, compositions in accordance with this invention containing the same straight mineral lubricating oil base and molybdate corrosion inhibitors gave as little as 2.5 milligrams weight loss. In the caseof the conventional compounded mineral lubricating oils of the internal combustion engine type, the improvement was even more remarkable. The diflerent compounded oils alone gave copper-lead strip weight losses ranging as high as 253 milligrams whereas the lubricating oil compositions of this invention containing the same compounded base oil plus a glycol or polyhydroxy benzene complex of molybdi-c'acid resulted in very little corrosion loss, one being as low as 0.9 milligram.

' The performance"characteristics of the lubricating oil compositions of this invention are also illustrated by their evaluation in a number of engine tests. The engine test procedures and techniques, though conventionaland well known in the lubricating oil art, are briefly described for the sake of convenience in the following paragraphs along with the test data.

In the L-4 engine test the corrosion characteristics of theoils are determined in a Chevrolet standard 6-cylinder engine in a typical laboratory installation. Weighed copper-lead test bearings and new piston rings are installed. The test is run at a constant engine speed at about 300 R. P. M. under a load of brake horse-power for a total of 36 hours subsequent to a run-in period of 8 hours. The outlet temperature of the jacket coolant is 200 F. and the oil sump temperature is 280 F. At the conclusion of the test the engine is disassembled and inspected for varnish and sludge deposits and the various parts are rated on a cleanliness scale of 0 to 10. The bearings are weighed to determine the weight loss per whole bearing due to corrosion. Illustrative test results on the compositions of the invention using compounded oil (A) as described above are given in the following table:

The piston rating was 9.9 on a cleanliness scale of 0'to 10 and the total engine varnish and sludge deposit rating was 98.0 on a scale of 0 to 100. Not only-isthe test oil A 7 of the composition of the invention eiiective in reducing the bearing'corrosion loss from more than 500 milligrams to less than 100 milligrams per bearing, but it also gives a very high performance rating so far as engine cleanliness and varnish and sludge deposits are concerned.

Inthe Ll engine test the detergency characteristics of the lubricating oil compositions of the invention are evaluated in a single cylinder Caterpillar diesel test engine. The pistonrings, cylinder liner, valves, etc. are standard production units of the diesel type. The engine-is operatedat a speed of IOOOR. P. M. under a load of approximately 20 brake horse-power. The outlet jacket temperature of the coolant,is.175 -.180 F. and the'oil temperature'to the bearings is 145-150 F. After 120 hours operation with 0.4 percent sulfur-containing fuel, the engine is inspected for cleanliness. Compounded oil,(A), the reference oil, i s the sarne as described above. Illustrative test data are set'out in the following tabler Theabove test data show that the lubricating oil compositions of the invention are excellent diesel engine lubricating oils'of the heavy duty type.

The Ll and L4 engine tests referred to above are more fully described in the C. R. C. Handbook, 1946 edition, Coordinating Research Council, New York, New York. J

In' the Navy propulsion load test described in Mil. P-l7269 (Ships) 17 July 1952, the compositions of the invention are evaluated as diesel engine lubricating oils under severe operating conditions. The tests are run in a General Motors 4-cylinder diesel engine using one percent sulfur'fuel. Copper-lead bearings are employed. The. tests are run at a constant speed of 1800 R. P. M. under a load of 30 brake horse-power per cylinder. The crankcase temperature is 250 F. The present test is run continuouslyv to simulate railroad diesel engine performance unlike the standard Navy test procedure which permits regular 4-hour shutdown periods. Sea water was also excluded for the same reason. Compounded oil (A), the reference oil, is the same as described above. Test results are as follows:

The performance of the lubricating oil compositions of the invention is also evaluated by the Navy Series B. Test. This test is more fully described in Mil. P-l7273 (Ships) July 1952. The test conditions are similar to those of the Navy propulsion load test given above except that normal operating conditions are maintained. Copper: lead bearings. are employed. Compounded oil (A), the reference oil, is the same as described above. Illustrative testresults are as follows; 7

1 Table VI 7 .Weight Loss, mgs.

reference oil--.

in both of the Navy engine tests shown above, the bearing weight loss due to corrosion by the reference oil, a conventional heavy duty compounded oil, was extremely high. Such an. oil would be impossible to use for any prolongedperiod of time without shutdown. By way of distinction, the lubricatingoil composition of the invention containing molybdate complexes gives remarkably low corrosion losses after as much as 300 hours-of continuous operation. Greatly extended periods of troublefree operation of diesel engines are thus possible with these'improved oils.

Since, as, noted above, silver metal-containing bearings are more and more common in diesel engines, the corrosive effect of the lubricating oil compositions of the invention on silver bearings is'determined in comparison with a conventional oxidation and corrosion inhibited compounded lubricating oil. This test is run in a 4-cylinder diesel engine using one percent sulfur fuel. The procedure is the same as outlined in the Navy Series B tests given above. The conventional oxidation and corrosion inhibited compounded oil is a solvent refined SAE 40 viscosity mineral lubricatingoil having a viscosity index of 60. It contains 10 mM./kg. of zinc dialkyl dithiophosphate and 0.25 percent by Weightof a sulfurized diparaffin sulfide. Compounded oil (A), the uninhibited reference oil previously described and shown to be highly corrosive to copper-lead bearings, is also evaluated. Illustrative test results are given in the following table:

20 mMJkg. 2ethyl-1,3-hexanediol molybdat reference oil 7 V From the above test data it will be seen that the conventional oxidation and corrosion inhibited compounded lubricating oil causes a much greater silver bearing weight loss than the lubricating oil compositions of the invention. Although the weight losses of both compounded oil (A), the reference oil, and the compositions of the invention are low, it must be borne in mind that the reference oil has been shown to be unsatisfactory in the copper-lead bearing tests set out above. It is a further fact that, aside from corrosion losses, silver metal-containing bearings are extremely sensitive to lubricant compositions containing active sulfur type corrosion inhibitors and such compositions generally provide an unsatisfactorily low degree of lubricity for silver bearing surfaces.

The effectiveness of the lubricating oil compositions of the invention as antioxidants in conventional engine oil compositions is also determined in a series of oxidation tests. In these tests the oil is maintained at a temperature of 340 F. under a pressure 'of one atmosphere of oxygen. During the test the oil is agitated by a high speed glass stirrer and the amount of oxygen added is recorded. An oxidation catalyst in the amount of 0.1 percent by weight iron naphthenate and 0.1 percent by weight copper naphthenate is added. The oxidation rate in cubic centimeters of oxygen per grams of oil per hour is meastired. Compounded oil (A) is the same oil asdescribed The antioxidant properties of the lubricating oil compositions of the invention are also evaluated in tests for determining the oxidation inhibition period. In these tests the oil is contained in a large glass tube equipped with a high speed glass stirrer. The oil temperature is 340 F. and a pressure of about one atmosphere of pure oxygen is maintained. The volume of oxygen added is automatically recorded and the time in hours required for 100 grams of oil to absorb 1200 cc. of oxygen is called the inhibition period. Illustrative test results are as follows:

Table IX Inhibition Oil Period in Hours Heavy medicinal white 011 (reference oil). 0.0 0.2% by weight 2-ethyl-l,3-hexane-diol m bdate in refer ence oil 0. 9 1 0.2% by weight 2-ethyl-1,3-hexane-diol molybdate and 0.2% by weight phenyl-a-naphthylamine in reference oil. 64. 0.2% by weight 2-ethy1-1,3-hexane dio1 molybdate and 2% by weight i t butylcatechol in reference oil 6. 3 0.2% by weight phenyl-a-naphthylamine in reference oil." 3. 3 0.2% by weight 4-t-butylcatechol in reference oil 2. 7

The test data of the above tables show that lubricating oil compositions containing the complexes of the invention are effectively inhibited against oxidation whereas similar lubricating oil compositions without the molybdic acid compiexes are susceptible to a very high rate of oxidation. The test results of the above tables also show that when conventional oxidation inhibitors of the diaryl amine and polyhydroxy benzene type illustrated by phenyl-a-naphthylamine and 4-t-butylcatechol, respectively, are employed in the compositions according to this invention, a marked improvement in the effect of the primary oxidation inhibitor is obtained, indicating synergism of the conventional antioxidant and the molybdate.

Other conventional oxidation inhibitors of the diaryl amine type which are suitable for employment in the improved compositions of the invention include p-hydroxy diphenyl amine, p,p'-dihydroxy diphenyl amine, diphenyl-p-phenylene diamine, diphenyl amine, phenothiazine, di-fl-naphthylamine, etc. Other polyhydroxy aromatic compounds include 1,2-dihydroxy naphthalene, hydroquinone, di t butyl resorcinol, 1,2 dihydroxy- 4-amino naphthalene, etc. Other oxidation inhibitors of these general types are also well known in the art.

In the compositions of the invention including both conventional oxidation inhibitors and the molybdates, any amount of the conventional inhibitor sufiicient to inhibit oxidation and any amount of the molybdate sufficient to enhance the action of the conventional inhibitor may be employed. Ordinarily, amounts of from 0.1 to 5.0 percent by weight of the composition of the conventional inhibitor and the molybdate each are sufficient. Preferably from 0.05 to 2 percent by weight of each inhibitor is employed in operations where there is little danger of encountering extremely high temperatures.

The amounts of conventional inhibitor and molybdate need not be the same in any given composition.

The nature of the improved lubricating oil compositions of the invention and their effectiveness should be readily apparent from the many illustrations given above.

are not adversely affected. This is indeed remarkable since the problem of devising lubricant compositions uniformly noncorrosive to both types of bearing metals has long confronted workers in the art. As shown by the actual tests set out above, the advantages of these improvernents are obtained without loss of other desirable properties of the lubricant compositions.

As mentioned above, the molybdenum compounds of the compositions according to this invention are preferably formed from molybdic acid or salts thereof and an alphaor beta-diol or vicinal dihydroxy benzene. Although the present invention is in no way limited to any theory concerning the structure of the compounds, it is believed that they may be illustrated by the followinng formulae:

Mono-glycol molybdates Pyrocatechol molybdates wherein R is hydrogen or a group of hydrocarbon structure as previously described. The formulae shown here represent the acid anhydride forms of these materials. By reaction with water these materials can readily be converted to the acid forms.

Although the above types of compounds are distinctly preferred in the compositions of the invention, other compounds of similar structure having substituents on the hydrocarbon groups which do not adversely aifect the reaction may likewise be employed. Such substituents include: hydroxyl groups, as when a polyhydroxy alcohol or benzene such as glycerol, pentaerythritol, sorbitol or trihydroxy benzene is used; ester groups, as when glycerol monooleate or sorbitan monooleate is used; and halogens, ethers, amides, etc., as will be apparent to those skilled in the art from the above description of the invention.

Although the compositions of the invention have been primarily described as crankcase lubricants for internal combustion engines, they are also useful as turbine oils, hydraulic fluids, instrument oils, constituent oils in grease manufacture, ice-machine oils, and the like.

Although the complexes of molybdic acid with glycol or polyhydroxy benzene, as described above, are distinctly superior and provide the preferred lubricating oil compositions of the invention, various amine salts of the molybdic acid complexes may also be employed advantageously. These amine salts are prepared by heating a mixture of the complex of molybdic acid with glycol or polyhydroxy benzene and an organic amineisuchfas trimethyl amine, triethanol amine, lauryl amine, phenyl- (x-naphthylamine, meta-xylylene diamine, :para-xylylene diairiine, amino phenol, pyridine,morpholine; 'etc': Other substituted molybdates which also may be employed include the esters of the molybdic acid complexes such as the monobutyl ester of di(2-ethylhexanediol-1,3 molybdate, monopentaerythritol di(2 ethylhexanediol 1,3) molybdate, etc. I T j The effectiveness of the lubricating oil compositions containing an amine salt of a molybdic acid complex as illustrated above is determined in the copper-lead strip corrosion test previously described in this specification. The reference oil in this case is a compounded oil comprising a solvent refined SAE 40 mineral lubricating oil base having a viscosity index of 60 and containing 10 mM/kg. of neutral calcium petroleum sulfonate and 20 mM./ kg. of calcium alkyl phenate, sulfurized. Results of the test are as follows:

Table X Copper-Lead Oil Strip Weight Loss (mgs.)

Oompounded oil (reference oil) 253. 1

20 mMJkg. octylene glycol molybdate 2 ethylhexylamlue salt in ref. oil a 3. 6 20 mM./kg. ethylene glycol molybdate Z-ethylhexylamine salt in ref. oil 6. 40 mM./kg. Z-ethylhexylamine in ref. oil 560. 7

The effectiveness of the derivatives of the molybdic acid complexes as corrosion inhibitors is readily apparent from the above test results. Very little weight loss is obtained with compositions containing the glycol molybdateamine salts whereas the uninhibited reference oil alone gives an objectionably high corrosion weight loss. The fact that the excellent effects obtained by the use of the compositions of the invention are not due merely to a simple addition of the amine is also illustrated by the test data. Although Z-ethylhexylamine salts of the molybdates give corrosion losses as low as 3.6 milligrams, the 2-ethylhexylamine alone in the same reference oil results in a very high corrosion loss of over 560 milligrams.

We claim:

1. A lubricant composition comprising an oil of lubricating viscosity and a molybdic acid complex of a member of the. group consisting of ocand B-alkane diols of 2 to 18 carbon atoms and alkyl vincinal dihydroxy benzenes containing from 2 to 18 carbon atoms in the alkyl group, said molybdic acid complex being in an amount suflicient to inhibit corrosion. v 2. A lubricant composition comprising an oil oflubricating viscosity and a molybdic acid complex of analkyl vicinal dihydroxy benzene containing from 2 to 18 carbon atoms in the alkyl group in an amount sufiicient to inhibit corrosion.

3. A lubricant composition comprising an .oil of lubri: eating viscosity and a molybdic acid complex of an o;- alkane diol of 2 to 18 carbon atoms in an amount sufiicient to inhibit corrosion. v

4. A lubricant composition comprising an oil of lubricating viscosity and a molybdic acid complex of a flalkane diol of 2 to 18 carbon atoms in an amount sufficient to inhibit corrosion.

5. A lubricant composition comprising an oil of lubricating viscosity and 0.01 to 5.0 percent by weight based on the oil of a molybdic acid complex of 2-ethylhexanei- 1,3-diol. c j

6. A lubricant composition comprising an oil of lubricating viscosity and from about 0.01 to about 5.0 percent by Weight based on the oil of a molybdic acid complex of 4-tert.-buty1 pyrocatechol. 7. A lubricant composition comprising a mineral lubri:

cating oil for internal combustion engines which is normally corrosive to alloy'be'arings and a molybdic acid complex of a member of the group consisting of aand fi-alkane diols of 2 to 18 carbon atoms and alkyl vicinal dihydroxy benzenes containing from 2 to 18 carbon atoms in the alkyl group, said molybdic acid complex being in complex of an walkane diolcontaining from2 to 18 carbon atoms in an amount sufiicient to inhibit corrosion.

10. A lubricant composition comprising a mineral lubricating oil for internal combustion engines which is normally corrosive to alloy bearings and a molybdic acid complex of a B-alkane diol containing from 2 to 18 carbon atoms in an amount suflicient to inhibit corrosion.

11. A lubricant composition comprising a mineral lubricating oil for internal combustion engines which is nor-j mally corrosive to alloy bearings and from about 0.01 to about 5.0 percent by weight based on the oil of. a molybdic acid complex of 2-ethylhexane-1,3-diol.

' 12. A lubricant composition comprising a mineral lubricating oil for internal combustion engines which is normally corrosive to alloy bearings and from about 0.01 to about 5.0 percent by weight based on the oil of a molybdic acid complex of 4-tert.-butyl pyrocatechol.

13. A lubricant composition comprising a mineral lubricating oil for internal combustion engines which is normally corrosive to alloy bearings and from about 0.01 toabout 5.0 percent by weight based on the oil of a molybdic acid complex of ethylene glycol. 14. A lubricant composition comprising a mineral lubricating oil for internal combustion engines which is normally corrosive to alloy bearings, from about 0.01 to about 5.0 percent by weight based on the oil of a molybdic acid complex of a member of the group consisting of ocand fi-alkane diols of 2 to 18 carbon atoms and alkyl vicinal dihydroxy benzenes containing from 2 to 18 carbon atoms in the alkyl group; and from about 0.01 to about 5.0 percent by weight based on the oil of a diaryl amine oxidation inhibitor.

References Cited in the file of this patent UNITED STATES PATENTS 2,144,654 Guthmann Jan. 24, 1939 2,161,184 McKone et a1. June 6, 1939 2,305,627 Lincoln et a1 Dec. 22, 1942 2,410,652 Grilfin et al. Nov. 5, 1946 2,465,296 Swiss Mar. 22, 1949

Claims

1. A LUBRICANT COMPOSITION COMPRISING AN OIL OF LUBRICATING VISCOSITY AND A MOLYBDIC ACID COMPLEX OF A MEMBER OF THE GROUP CONSISTING OF A-AND B-ALKANE DIOLS OF 2 TO 18 CARBON ATOMS AND ALKYL VINCINAL DIHYDROXY BENZENES CONTAINING FROM 2 TO 18 CARBON ATOMS IN THE ALKYL GROUP, SAID MOLYBDIC ACID COMPLEX BEING IN AN AMOUNT SUFFICIENT TO INHIBIT CORROSION.